1. Field of the Invention
This invention relates to a seat height adjustment apparatus for a motorcycle which makes it possible to adjust the height of a driver's seat of a motorcycle.
2. Description of Background Art
For a motorcycle, a footing property for a driver is demanded. The footing property depends upon the height from the ground to the driver's seat and the size of the body of the driver. Therefore, it is desired to provide a motorcycle with a seat height adjustment apparatus.
Various proposals have been made for a motorcycle provided with a seat height adjustment apparatus in related art. See, for example, Japanese Patent Laid-Open No. 2003-81157, FIGS. 19 and 21.
As shown in FIG. 19 of Japanese Patent Laid-Open No. 2003-81157, the seat height adjustment apparatus for a motorcycle includes a front cross plate 56 (this indicates a reference symbol applied in Japanese Patent Laid-Open No. 2003-81157 this similarly applies also to the description given below) fixed to a vehicle body frame, adjuster brackets 57 fixed to the front cross plate 56, adjust guides 59 disposed between two support plate portions provided on the adjuster brackets 57, a pin member 60 inserted in a slot 50 of the adjuster brackets 57 and a hole 59a of the adjust guides 59. Fixing members 56a, attached after washers 60a, are fitted to an end portion of the pin member 60 with a second pin member 62 inserted in a guide slot 58 of the adjuster brackets 57 and a second hole 59b of the adjust guides 59. In addition, fixing members 56a, attached after washers 60a, are fitted to an end portion of the second pin member 62.
Since another assembly of an adjuster bracket 57 and an adjust guide 59 is provided in a vehicle body widthwise direction in addition to the assembly shown, a single adjuster bar 61 is attached to the adjuster guides 59 of the two assemblies, and a spring 63 is attached between the adjuster bar 61 and the front cross plate 56. Further, the adjuster bar 61 is a member which engages with a projection 10A of a driver's seat 10. Now, the operation of the seat height adjustment apparatus is described.
As shown in FIG. 21(a) of Japanese Patent Laid-Open No. 2003-81157, in the seat height adjustment apparatus, since the pin member 60 is engaged with a lower stage of the slot 50 and the second pin member 62 is fitted in the guide slot 58, the adjuster bar 61 stops stationarily at a low position. On the other hand, at a rear portion of the driver's seat 10, a rear concave step 54 is fitted with a convex third supporting portion 53 provided on the vehicle body frame. If the projection (reference symbol 10A of FIG. 19 of Japanese Patent Laid-Open No. 2003-81157) of the driver's seat 10 is engaged with the adjuster bar 61, then the driver's seat 10 assumes a low position.
If the adjuster bar 61 is pulled rearwardly of the vehicle body once against the tensile force of the spring (reference symbol 63 of FIG. 19 of Japanese Patent Laid-Open No. 2003-81157) and then it is returned forwardly of the vehicle body so that the pin member 60 is engaged with a middle stage of the slot 50, then the adjuster bar 61 stops stationarily at an intermediate position as shown in FIG. 21(b) of Japanese Patent Laid-Open No. 2003-81157. Meanwhile, rearwardly of the driver's seat 10, since the central concave step 54 is fitted with the convex third supporting portion 53 on the vehicle body side, the driver's seat 10 assumes an intermediate position.
Similarly as in the seat adjustment described above, the pin member 60 is engaged with an upper stage of the slot 50 and, rearwardly of the driver's seat 10, the front concave step 54 is fitted with the convex third supporting portion 53 on the vehicle body side as shown in FIG. 21(c) of Japanese Patent Laid-Open No. 2003-81157. As a result, the driver's seat 10 assumes a high position.
In addition, since the seat height adjustment apparatus of Japanese Patent Laid-Open No. 2003-81157 has a great number of parts as shown in FIG. 19 of Japanese Patent Laid-Open No. 2003-81157, the cost required for working and assembly is high. It is further preferable that, even if the number of parts of the seat height adjustment apparatus is decreased, the height of the driver's seat 10 can be adjusted simply.
Therefore, a seat height adjustment apparatus for a motorcycle which includes a reduced number of parts and can adjust the height of a seat simply is in demand.